Diffractive Waveguide Optical Element for Wider AR Field of View
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Solution Overview
Problem
Current AR devices are limited by a field of view (FOV) of about 40 degrees due to the use of glass lenses with a refractive index of 1.7, which cannot be increased without significantly increasing cost, and the refractive index of transparent glass has an upper limit.
Innovation Solution
An optical element using a waveguide substrate with alternating high and low refractive index layers and sub-wavelength nanostructures to enhance image beam reflectance and guide it through total internal reflection, increasing the FOV to 60 degrees or more without high-cost high-refractive index glass lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If glass lens with higher refractive index is used to increase FOV, then FOV can be increased, but cost will increase correspondingly
Solution Approach 1:
The patent changes the refractive index parameter of the waveguide medium from conventional glass (n=1.7) to high refractive index material (n≥2.0), enabling FOV expansion to 60 degrees or more while avoiding the cost penalty associated with traditional high-index glass lenses
Solution Approach 2:
The patent employs composite material structures including multiple layers with different refractive indices (high refractive index waveguide layer, low refractive index cladding layers, and intermediate layers) to achieve both high FOV and cost-effectiveness, eliminating the need for expensive monolithic high-index glass
2Ease of manufacture
If glass lens with refractive index of 1.7 is used, then cost is controlled, but FOV is limited to about 40 degree angle
Solution Approach 1:
The patent fundamentally changes the refractive index parameter from 1.7 to 2.0 or higher, which directly enables the expansion of FOV from 40 degrees to 60 degrees or more while maintaining cost control through alternative material selection
3Area of stationary object
If transparent glass with higher refractive index is required, then FOV can be increased, but refractive index has upper limit and cannot increase without limit
Solution Approach 1:
The patent uses composite material systems with multiple layers having different refractive indices to achieve effective optical performance equivalent to or exceeding that of single-material high-index glass, thereby overcoming the refractive index upper limit of transparent glass
Solution Approach 2:
The patent extends the effective refractive index range by using material combinations and structural designs that provide optical properties beyond what single-phase transparent glass can achieve
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively increases the FOV to 60 degrees or more by reducing image beam leakage and maintaining cost-effectiveness, while allowing for flexible material selection beyond the refractive index limit of glass.
Implementation Method 1
The sub-wavelength nanostructure is configured to receive and diffract the image beam, so as to couple the image beam to the waveguide substrate
Implementation Method 2
configured to propagate the image beam between the first side and the second side of the waveguide substrate in a manner of total internal reflection
Implementation Method 3
The first optical film structure and the second optical film structure are configured to reflect a part of the image beam at an incident angle inside the waveguide substrate smaller than a critical angle of the waveguide substrate
Data Source
AI summary
An optical element includes a waveguide substrate, first and second optical film structures, and a sub-wavelength nanostructure. The waveguide substrate has first and second sides, a light entering surface and a light exiting surface. An image beam can enter the interior of the waveguide substrate through the light entering surface and travel in a manner of total internal reflection. The image beam exits the waveguide substrate via the light exiting surface after one or more reflections. The first and second optical film structures are respectively arranged on the first and second sides. The sub-wavelength nanostructure arranged on the first side can receive and diffract the image beam to couple the image beam to the waveguide substrate. The first and second optical film structures can reflect the part of the image beam at the incident angle smaller than the critical angle of the waveguide substrate.